1. Field of the Invention
This invention relates to a method of power management in a data replication process deployed in a wireless information device. The term ‘wireless information device’ used in this patent specification should be expansively construed to cover any kind of device with one or two way wireless information capabilities and includes without limitation radio telephones, smart phones, communicators, personal computers, computers and application specific devices. It includes devices able to communicate in any manner over any kind of network, such as GSM or UMTS, CDMA and WCDMA mobile radio, Bluetooth, IrDA etc.
2. Description of the Prior Art
Data replication processes are deployed in wireless information devices to replicate information held on a wireless information device onto a remote server; replication from the server to the wireless device is also possible. Typical applications that use data replication are for synchronisation of files (e.g. address/contacts lists; diary contents) and also messaging. Another increasingly popular application is the uploading of photographs from the wireless device to a photo sharing site; the Shozu™ service from Cognima is one such application.
In the Shozu service, when an object within the photo database on the phone is changed, the change is queued for transfer to the remote server over a wireless link (typically the cellular wireless network). Normally, that object is transferred to the server as soon as a data connection is available.
Details of the replication protocol used in Shozu can be found in GB2384589B or US 2005-0021571, the contents of which are incorporated by reference. Appendix 1 also includes details of this replication system. One disadvantage of this approach is that it can rapidly deplete the power reserves of the wireless information device.
There are several power management strategies commonly used in wireless information devices to preserve battery life, including causing the device to shut down (i.e. enter a low power consumption state) when not in use, referred to as going into a ‘sleep’ mode, and by causing devices such as cellular telephones to camp, i.e., cycle on and off many times a minute, switching on only very briefly to determine if a call or message is being transmitted to the cellular telephone.
Certain types of electronic data storage, for example random access memories or RAM, typically require that the device retain some electrical charge in its batteries to preserve stored data—if the battery is completely discharged, the data will be lost. To avoid loss of data, it is therefore common for such electronic devices to shut down completely before a certain minimum safe battery charge is reached. Alternatively, some devices, have a secondary battery to protect memory—though this device also shuts down at a minimum battery charge. While such shut-down arrangements are an effective way of protecting memory, they are extremely irritating to users, since they necessarily inhibit access to the functions of the device; premature shut down, i.e., a shut down before a critical battery energy level is reached, is yet more irritating and therefore undesirable.